Large-scale infrastructure systems, providing essential goods and services to our societies and economies, are witnessing tighter integration and coupling, notably by the sheer ubiquitous use of cyber-physical systems for integration, communication, and control. Putting the electric power system in focus, the pertinent supervisory and data acquisition systems are not only running through major changes allowing for increased levels of communications but also exposing them to new (cyber) threats. Furthermore, humans are an essential part of these systems interacting with them and developing them into a ''system of socio-technical systems''. In theory, and evidenced by past blackouts, power grids show complex behaviors and a strong influence of contextual factors. While the deterministic ''N-1 security principle'' has been successful in ensuring high performance of the European grid, it has been deemed insufficient to cope with multiple failures, cascading grid tripping scenarios, and non-technical factors and to capture a widened spectrum of threats. Thus, as traditional models often reach their limits, advanced modeling and simulation techniques are necessary, which are partly available and applied. Moreover, past disasters prove the need of focusing on ''after shock behavior'' and precaution against unanticipated events by amplifying absorptive, adaptive, and recovery capabilities. This shift towards increased resilience requires substantial conceptual work and the further development of analytical tools. Here the latest achievements and future challenges in this field of active research, aiming at securing the operation of those systems, are highlighted.